1. Field of the Invention
This invention relates to a process of producing an ion exchanger for adsorbing mercury ion and the like using wood materials. It is an object of this invention to provide processes for producing low-cost adsorbents which can remove mercury ion from waste water.
2. Summary of the Invention
According to this invention a process for producing an ion exchanger for adsorbing mercury ion includes the steps of impregnating a xanthated wood meal, which has been prepared by well-known methods with a peroxide polymerization initiator to produce active radicals thereon, graft copolymerizing said xanthated wood meal having active radicals with acrolein in gas phase under reduced, atmospheric or high pressure within an autoclave at a temperature of 20.degree. C. to 70.degree. C., preferably at 50.degree. C., to introduce aldehyde groups, and then converting said aldehyde groups to thiosemicarbazone groups at ordinary temperature under atmospheric pressure to generate radicals capable of ion exchange.
One feature of the process according to this invention is that the graft copolymerization of acrolein proceeds at a high rate of reaction, and can be performed without danger as the reaction takes place at a low temperature. Another feature of this invention is that unreacted monomers can be easily recovered. An important characteristic of the ion exchangers obtained by the process according to this invention is the fact that they adsorb selectively mercury ion to be separated from other metal ions and the recovery of mercury ion can be easily performed. In addition, the production cost of the ion exchangers is characteristically low.
The particle size of starting wood meal is preliminarily regulated to have a particle size of 40 to 60 mesh, and then the wood meal is purified by a pretreatment involving extractions with warm water, alcohol, benzene or the like. However, such pretreatment can be omitted when certain starting materials are employed.
Generally the wood material is capable of limited swelling, and this property is maintained by the xanthated wood material used as the starting material in the present invention. The limited swelling property means that the material will not be disintegrated into single fibers and will maintain the original textural structure.